The present invention relates to a method and apparatus for applying a sizing composition to glass fibers.
Glass fibers are useful in a variety of technologies. A common application of glass fibers is as reinforcements in polymer matrices to form glass fiber reinforced plastics or composites. The manufacturing of glass fibers begins by providing molten glass to a heat-resistant platinum tray called a xe2x80x9cbushing.xe2x80x9d The bushing has a plurality of orifices through which the molten glass flows to become filaments. The filaments are then coated with a size, aqueous or nonaqueous, via an applicator roll. The sizing on the filaments protects the filaments during processing and handling and also serves as a polymer reinforcement by ensuring the adhesion of the glass filaments to the resin material. Finally, after the sizing is applied, the filaments are gathered together into strands at what is known as a gathering shoe and wound on a collet to produce a glass fiber package.
U.S. Pat. No. 4,537,610 discloses an applicator for applying a nonaqueous sizing composition to glass fibers. The applicator includes a driven roll which receives sizing from a chamber and applies the sizing to the surface of glass fibers which are drawn across it. One problem common to applicators having driven rolls is xe2x80x9cfiber wrap.xe2x80x9d This problem occurs when the fibers adhere to the surface of the size-coated driven roll such that the fibers become wrapped about the roll. Such a problem is costly as it results in a shutdown of the fiber forming process.
Accordingly, there is a need for an improved apparatus for applying a nonaqueous sizing composition to glass fibers.
This need is met by the present invention whereby an improved apparatus is provided for applying a nonaqueous sizing composition to glass fibers.
In accordance with a first aspect of the present invention, a sizing applicator is provided for applying a coating of sizing composition to reinforcement fibers. The sizing applicator comprises an applicator element including a main body portion having at least one recess for receiving a replaceable insert and sizing supply apparatus positioned adjacent to the applicator element for supplying a sizing composition to the applicator element. The applicator element is adapted to be positioned such that the insert is engaged by reinforcement fibers drawn across the applicator element. The applicator element applies a coating of the sizing composition to the reinforcement fibers drawn across the applicator element.
The main body portion may include two or more recesses and the applicator element may include two or more inserts.
The main body portion is rotatable to permit a worn insert to be rotated away from the path of the reinforcement fibers and to allow an unused insert to be positioned in that path. Rotation of the main body portion may occur during a fiber forming process.
An indexing mechanism, either motor driven or manually operated, may be provided for effecting rotation of the main body portion.
Preferably, the inserts are formed from a wear-resistant material, such as graphite, graphite coated stainless steel, or a phenolic resin and graphite composite including a lubricant additive such as teflon.
The sizing supply apparatus may comprise a sizing supply source and a housing having a supply port for receiving sizing composition from the sizing supply source and a passage extending from the supply port to an exit slot. The passage comprises a cavity which communicates with the supply port and a passageway extending from the cavity and terminating at the exit slot. The passage receives the sizing composition from the supply port and delivers the sizing composition to the exit slot. The applicator element is supported by the housing and positioned to receive the sizing composition discharged at the exit slot.
The sizing supply source comprises a reservoir for storing sizing composition to be applied to the reinforcement fibers, and pumping apparatus coupled to the reservoir and the housing supply port for transferring the sizing composition from the reservoir to the housing supply port. The pumping apparatus comprises first and second conduits and a metering pump. The first conduit is coupled to the reservoir and the metering pump and the second conduit is coupled to the metering pump and the supply port. The reservoir is preferably positioned relative to the applicator element so as to capture excess sizing composition falling from the applicator element. The sizing supply source may further include a screen provided in the reservoir for filtering contaminants from the captured sizing composition to permit the captured sizing composition to be reused.
The sizing supply source preferably further comprises a level sensor for sensing when the sizing composition in the reservoir has fallen below a predetermined level. Fill apparatus may be provided for supplying additional sizing composition to the reservoir when the level sensor indicates that the sizing composition in the reservoir is below the predetermined level. The fill apparatus comprises a fill pump, a size supply tank, a first conduit extending from the tank and coupled to the fill pump and a second conduit coupled to the fill pump and extending to the reservoir.
In accordance with a second aspect of the present invention, a sizing applicator is provided for applying a coating of sizing composition to reinforcement fibers. The sizing applicator comprises an applicator element and sizing supply apparatus positioned adjacent to the applicator element for supplying a sizing composition to the applicator element. The applicator element applies a coating of the sizing composition to reinforcement fibers drawn across the applicator element. The sizing supply apparatus includes a sizing supply source and a housing for receiving sizing composition from the sizing supply source. The sizing supply source comprises a reservoir for storing the sizing composition to be applied to the reinforcement fibers and is positioned relative to the applicator element so as to capture excess sizing composition falling from the applicator element. The sizing supply source further includes a screen in the reservoir for filtering contaminants from the captured sizing composition to permit the captured sizing composition to be reused.